Recent concerns about security of energy resources and global warming have let to increased focus on the use of biofuels as a renewable resource. Biodiesel has been produced for 15 to 20 years and, until recently, has mainly been produced in Europe and mostly from rapeseed oil.
In recent years biodiesel production in the USA has increased significantly. With the expansion of biodiesel production in the USA, an increasing amount of soy oil (and/or other oils which contain varying amounts (sometime minor amounts) of steryl glycoside) is/are being used as a raw material for the biodiesel production.
It has recently come to light that biodiesel and biodiesel blends made from oil containing steryl glycoside can cause problems. For example, the presence of steryl glycoside in a biofuel may cause precipitation therein which is undesirable as it may result in filter clogging and/or causing an engine fuelled by the biofuel to stop. Precipitation may be the precipitation of the steryl glycoside or may be the precipitation of the steryl glycoside in combination with other components within the biofuel. It has been suggested that precipitation of the steryl glycosides may exacerbate precipitation and/or aggregation of other components in the biofuel.
The steryl glycoside may precipitate during storage over the course of several weeks. Therefore, although freshly produced biodiesel may meet the quality standards, after some week's storage the biodiesel may no longer pass the filter test.
It has been found that steryl glycoside is not easy to remove during production of biofuel (including biodiesel).
Producers of biodiesel have tried to overcome these problems by additional filtration steps and by centrifugation.
WO2007/076163 relates to the use of specific filtration procedures to remove steryl glycoside. In particular WO2007/076163 discloses a process for removing steryl glycosides from biodiesel by adding adsorbents, filter aids, boric acid, soap, sucrose, sugar, glucose, sodium chloride, citric acid, magnesium silicate, clay, diatomaceous earth, lecithin, granular clay, granular glucose, granular sugar, protein, textured vegetable protein, carbon, cellulose, solutions comprising boric acid, silica hydrogel and combinations thereof that are allegedly capable of removing steryl glycosides from the biodiesel. One disadvantage of this procedure is that it introduces an extra filtration step which can be costly and/or time consuming.
Another disadvantage of removing steryl glycosides by filtration or centrifugation is that it may be necessary to wait for the steryl glycosides to precipitate and/or aggregate before they can be removed from the oil.
The present invention aims to overcome a problem related to the presence of steryl glycoside in biofuels.